Method for guiding a crack in the peripheral region of a donor substrate

Abstract

The present invention relates to a method for separating solid-body slices ( 1 ) from a donor substrate ( 2 ). The method comprises the steps of: producing modifications ( 10 ) within the donor substrate ( 2 ) by means of laser beams ( 12 ), wherein a detachment region is predefined by the modifications ( 10 ), along which detachment region the solid-body layer ( 1 ) is separated from the donor substrate ( 2 ), and removing material from the donor substrate ( 2 ), starting from a surface ( 4 ) extending in the peripheral direction of the donor substrate ( 2 ), in the direction of the center (Z) of the donor substrate ( 2 ), in particular in order to produce a peripheral indentation ( 6 ).

The invention claimed is: 
     
       1. A method for separating at least one solid-body layer, in particular a solid-body slice ( 1 ), from a donor substrate ( 2 ), said method comprising at least the following steps:
 providing a donor substrate ( 2 ), 
 firstly, producing modifications ( 10 ) within the donor substrate ( 2 ) by means of LASER beams ( 12 ), wherein a detachment region is predefined by the modifications ( 10 ), along which detachment region the solid-body layer ( 1 ) is separated from the donor substrate ( 2 ), 
 then removing material from the donor substrate ( 2 ) starting from a surface ( 4 ) extending in the peripheral direction of the donor substrate ( 2 ) in the direction of the centre (Z) of the donor substrate ( 2 ), in particular in order to produce a peripheral asymmetrical indentation ( 6 ), 
 wherein the detachment region is exposed by the material removal, 
 separating the solid-body layer from the donor substrate, 
 wherein the donor substrate is weakened in the detachment region by the modifications in such a way that the solid-body slice ( 1 ) detaches from the donor substrate ( 2 ) as a result of the material removal or a stress-inducing layer ( 14 ) is produced or arranged on a surface ( 16 ) of the donor substrate ( 2 ), in particular a planar surface, oriented at an incline relative to the peripheral surface, and mechanical stresses are produced in the donor substrate ( 2 ) by a thermal treatment of the stress-inducing layer ( 14 ), wherein the mechanical stresses produce a crack ( 20 ) for separating a solid body layer ( 1 ), which crack propagates along the modifications ( 10 ), starting from the surface of the donor substrate exposed by the material removal. 
 
     
     
       2. The method according to  claim 1 , characterised in that the detachment region predefined by the modifications ( 10 ) is distanced further from the peripheral surface of the donor substrate ( 2 ) prior to the material removal than after the material removal. 
     
     
       3. The method according to  claim 2 , characterised in that:
 the modifications ( 10 ) for predefining the detachment region are produced prior to the material removal, and by means of the material removal a reduction of the distance of the detachment region to less than 10 mm, in particular to less than 5 mm and preferably to less than 1 mm, is achieved at least at specific points, or 
 the modifications for predefining the detachment region are produced after the material removal, wherein the modifications ( 10 ) are produced in such a way that the detachment region is distanced, at least at specific points, by less than 10 mm, in particular less than 5 mm, and preferably less than 1 mm, from a surface exposed by the material removal. 
 
     
     
       4. The method according to  claim 3 , characterised in that:
 the material is removed by means of ablation beams ( 8 ), in particular ablation LASER beams, or ablation fluid, or 
 an indentation ( 6 ) with an asymmetrical design is produced by the material removal, or 
 the material removal is performed at least in portions in the peripheral direction of the donor substrate ( 2 ) as a reduction of the radial extent of the donor substrate ( 2 ), in the entire region between the detachment region and a surface of the donor substrate ( 2 ) distanced homogeneously from the detachment region. 
 
     
     
       5. The method according to  claim 4 , characterised in that the material to be removed in the entire region between the detachment region and the surface distanced homogeneously from the detachment region describes an annular, in particular cylindrical design. 
     
     
       6. The method according to  claim 4 , characterised in that the indentation ( 16 ) surrounds the donor substrate ( 2 ) completely in the peripheral direction. 
     
     
       7. The method according to  claim 6 , characterised in that the indentation ( 6 ) runs towards the centre (Z) as far as an indentation end ( 18 ) in a manner becoming increasingly narrower, in particular in a wedge-like manner, wherein the indentation end ( 18 ) lies in the plane in which the crack ( 20 ) propagates. 
     
     
       8. The method according to  claim 7 , characterised in that the asymmetric indentation ( 6 ) is produced by means of a grinding tool ( 22 ) that is negatively shaped at least in part in order to make the indentation ( 6 ). 
     
     
       9. The method according to  claim 8 , characterised in that the grinding tool ( 22 ) has at least two differently shaped processing portions ( 24 ,  26 ), wherein a first processing portion ( 24 ) is intended for processing of the donor substrate ( 2 ) in the region of the underside ( 28 ) of a solid-body slice ( 1 ) to be separated and a second processing portion ( 26 ) is intended for processing of the donor substrate ( 2 ) in the region of the upper side ( 30 ) of the solid-body slice ( 1 ) to be separated from the donor substrate ( 2 ). 
     
     
       10. The method according to  claim 9 , characterised in that the first processing portion ( 24 ) produces a deeper or larger-volume indentation ( 6 ) in the donor substrate ( 2 ) than the second processing portion ( 26 ), wherein the first processing portion ( 24 ) and/or the second processing portion ( 26 ) have/has curved or straight grinding faces ( 32 ,  34 ). 
     
     
       11. The method according to  claim 9 , characterised in that:
 the first processing portion ( 24 ) has a curved main grinding face ( 32 ) and the second processing portion ( 26 ) has a curved secondary grinding face ( 34 ), wherein the radius of the main grinding face ( 32 ) is greater than the radius of the secondary grinding face ( 34 ), the radius of the main grinding face ( 32 ) is preferably at least twice as large as the radius of the secondary grinding face ( 34 ), or 
 the first processing portion ( 24 ) has a straight main grinding face ( 32 ) and the second processing portion ( 26 ) has a straight secondary grinding face ( 34 ), wherein, by means of the main grinding face ( 32 ), more material is removed from the donor substrate ( 2 ) than with the secondary grinding face ( 34 ), or 
 the first processing portion ( 24 ) has a straight main grinding face ( 32 ) and the second processing portion ( 26 ) has a curved secondary grinding face ( 34 ), or 
 the first processing portion ( 24 ) has a curved main grinding face ( 32 ) and the second processing portion ( 26 ) has a straight secondary grinding face ( 34 ). 
 
     
     
       12. The method according to  claim 11 , characterised in that the ablation LASER beams ( 8 ) are produced with a wavelength in the range between 300 nm and 10 μm, with a pulse length of less than 100 microseconds and preferably less than 1 microsecond, and particularly preferably less than 1/10 of a microsecond, and with a pulse energy of more than 1 μJ and preferably more than 10 μJ. 
     
     
       13. The method according to  claim 1 , characterised in that:
 wherein the LASER beams ( 12 ) are emitted from a LASER device ( 46 ), 
 wherein the LASER device ( 46 ) is a picosecond laser or a femtosecond laser, and/or 
 the energy of the LASER beams ( 12 ), in particular of the fs-LASER, is selected in such a way that the propagation of damage of each modification ( 10 ) in the donor substrate ( 2 ) is less than 3 times the Rayleigh length, preferably less than the Rayleigh length, and particularly preferably less than a third of the Rayleigh length, and/or 
 the wavelength of the LASER beams ( 12 ), in particular of the fs LASER, is selected in such a way that the absorption of the donor substrate ( 2 ) is less than 10 cm−1 and preferably less than 1 cm−1 and particularly preferably less than 0.1 cm−1, and/or 
 the individual modifications ( 10 ) are produced in each case as a result of a multi-photon excitation brought about by the LASER beams ( 12 ), in particular of the fs LASER. 
 
     
     
       14. The method according to  claim 1 , characterised in that the LASER beams ( 12 ) for production of the modifications ( 10 ) penetrate the donor wafer ( 2 ) via a surface ( 16 ) that is part of the solid-body slice ( 1 ) to be separated. 
     
     
       15. The method according to  claim 14 , characterised in that that the stress-inducing layer ( 14 ) comprises a polymer, in particular polydimethylsiloxane (PDMS), or consists thereof, wherein the thermal treatment is performed in such a way that the polymer experiences a glass transition, wherein the stress-inducing layer ( 14 ) is temperature-controlled, in particular by means of liquid nitrogen, to a temperature below room temperature or below 0° C. or below −50° C. or below −100° C. or below −110° C., in particular to a temperature below the glass transition temperature of the stress-inducing layer ( 14 ). 
     
     
       16. The method according to  claim 15  characterised in that the ablation radiation comprises accelerated ions and/or plasma and/or LASER beams and/or is formed by electron beam heating or ultrasound waves and/or is part of a lithographic method (electron beam, UV, ions, plasma) with at least one etching step following a previously executed photoresist coating and/or the ablation fluid is a liquid jet, in particular a water jet of a water jet cutting process.